This invention concerns a system realized by using a plurality of network connected computers.
In recent years the volume of data provided by computers providing a service over a network and the number of users using these computers via a network has increased substantially in line with the increased diffusion throughout society of networks such as the Internet.
However, with conventional concentrated type computer systems in which a single computer manages all data required by a user the processing capabilities of the computers are limited and it is not possible to exceed those performance limits and provide all users with the data they require. The storage capacity of the storage devices connected to such computers is limited, moreover if there is computer failure it is not possible to access data.
This invention discloses technology for a dispersed type of computer system that solves these problems.
The technology disclosed in Document 1 “OceanStore, an Architecture for Global-Scale Persistent Storage,” John Kubiatowicz et al., appearing in Chapter 2 of Proceedings of the Ninth International Conference on Architectural Support for Programming Languages and Operating Systems (ASPLOS 2000), November 2000 provides for placement and replication of data in each of a plurality of storage devices and servers installed in geographically dispersed locations (hereinafter referred to as “sites”). This allows the load for data processing and the data itself to be dispersed through a plurality of servers. Further, if any of these servers fails the data can be reconstructed using replicated data in other servers.
Hereinafter, any conglomeration of data like a program for example used by a user or a computer is referred to as a “file.”
Conventional concentrated management computer systems and the server infrastructure environment with servers dispersed on a global scale as disclosed in Document 1 allow a plurality of users to access files managed by computers. In order to ensure security under such an environment access rights to files must be set for each user of the system. Moreover, in order to accommodate the various uses demanded by the many users, it may be necessary to set file attributes as conditions dictate in response to such uses for each individual file in such a computer system.
With conventional programs (hereinafter “file systems”) managing files run by a computer, the types and number of file attributes that can be set for a file are limited. Further, as file attributes are managed and fixed for the entire file system it is not possible to increase or decrease the number and types of file attributes applicable to each individual file at will, so there is a lack of flexibility in file attributes management.
Moreover, when there are storage service providers performing services for storage and replication of files in storage devices managed by computers existing at a plurality of sites, different conditions for charges (hereinafter “accounting policy”) may be applied by providers for different storage devices managed by computers at each of those sites, thereby creating a demand to acquire information necessary for accounting (hereinafter “accounting information”) based on the relevant accounting policy. The only file attributes information that can be acquired with existing file systems is static information such as file capacity or the number of file accesses, while specific accounting information based on the accounting policy of a site, information on for example the type of storage device housing a file, cannot be collected.